Cutting plate for rotating tools

ABSTRACT

The invention relates to a cutting plate for tools rotating about a tool axis, especially boring tools with several cutting edges. Said cutting plate comprises a major cutting edge ( 26 ) which is connected to the minor cutting edge ( 32 ) in the radial extension thereof over a cutting corner ( 30 ) at a certain angle. A common face ( 38 ) is joined to a longitudinal side of the major cutting edge ( 26 ) and the minor cutting edge ( 32 ), while a major flank ( 40 ) or a minor flank ( 42 ) is joined to the other longitudinal side of the major cutting edge ( 26 ) and the minor cutting edge ( 32 ), said flank forming a wedge angle with said face. The aim of the invention is to be able to support the tool on the boring wall ( 36 ) with low friction in order to enable extensively vibration-free machining to be carried out even with long projecting tools. In order to achieve this, a support land ( 34 ) is arranged in the region of the minor cutting edge ( 32 ), said support land being defined by two interspaced support edges ( 44, 46 ) which are arranged in the rotating direction of the tool. The support edges have the same radial distance (r 1 , r 2 ) in relation to the tool axis ( 24 ) over the whole of the length thereof. Said support edges ( 44, 46 ) are oriented in a functionally parallel manner in relation to the tool axis ( 24 ), while the support land is functionally embodied in the form of a flat surface which is parallel in relation to the tool axis.

DESCRIPTION

[0001] The invention relates to a cutting plate for tools rotating abouta tool axis, in particular for boring tools with several cutting edges,comprising a major cutting edge and a minor cutting edge, which isconnected, in the extension of said major cutting edge radiallyoutwardly through a plate corner, at an angle to said major cuttingedge, comprising a common machining surface connected on onelongitudinal side of the major cutting edge and of the minor cuttingedge, and comprising one major flank or minor flank connected to theother longitudinal side of the major cutting edge or the minor cuttingedge, and defining a wedge angle with the common machining face.

[0002] In order to avoid vibrations during operation in far projectingtools with several cutting edges and with cutting plates of theaforementioned type, a minor cutting edge designed as a guiding edge isprovided which is guided along the bore wall. In order to achieve theguiding action, the guiding edge is usually provided with a circulargrinding, the radius of curvature of which is smaller than the radius ofthe bore. This means that the guiding edge is guided along a line on thebore wall. When the circular grinding has a radius which is too small,the guiding becomes relatively poor. The tool chatters because it getscaught on or cuts into the boring wall with the guiding edge. Whenapproaching the bore radius there occurs a surface contact, whichincreases the friction between the tool and the bore, and which canresult in overloads on the machine and/or the tools. The more cuttingedges that are arranged over the circumference of the tool, the moreserious this effect becomes.

[0003] Starting out from this, the basic purpose of the invention is toimprove the cutting plates of the above-identified type in such a mannerthat an optimum support action with a minimum friction results in thearea of the minor cutting edge.

[0004] To attain this purpose the characteristics disclosed in claim 1are suggested. Advantageous embodiments and further developments resultfrom the dependent claims.

[0005] The inventive solution is based on the thought that a supportland is arranged in the area of the minor cutting edge, which supportland is defined by two support edges arranged at a distance from eachother in the direction of rotation of the tool, which support edges arespaced over their entire length at the same radius distance forming atthe same time the flight-circle radius of the tool from the tool axis.Advantageously, the support edges thereby extend in their longitudinalextent parallel to the tool axis, whereas the support land providedbetween the support edges is designed preferably as a flat surface. Thesupport land advantageously has in its longitudinal extent alignedparallel to the tool axis a length, which length corresponds at least totwice the distance between the support edges. In order to obtain-aminimal friction support, the support edges should be spaced, dependingon the bore diameter, at a distance of 0.1 to 1.5 mm from each other.The support land between the support edges thereby advantageouslyextends over a fraction of the cutting-plate thickness. The support landextends in its longitudinal extent to the, if applicable, rounded orfaceted cutting-edge corner. The support edges can be faceted rounded orpreferably tangential to the tool flight circle. A preferred embodimentof the invention provides that the major cutting edge and the minorcutting edge designed as a support land define a right angle with eachother in their longitudinal extent.

[0006] The inventive cutting plate can be designed both as anexchangeable cutting plate with only one cutting-edge corner and also asan indexable insert with several cutting-edge corners. At least twomajor cutting edges and secondary cutting edges arranged at equalangular distances from each other are provided in the latter case. Thecutting plate is advantageously designed as a triangular-like insertwith three major cutting edges having a roof shape and a point angle of140 to 170°, whereby the support land, which is part of a major cuttingedge, is formed into the corner area of a major cutting edge adjacent ina defined index direction.

[0007] The inventive measures are suited both for use in solid drillsand also in core drills and reamers, and thereby are preferably usefulin far projecting or long tools with several cutting edges. The tendencyof the boring tool to vibrate is reduced by the minimal friction supportand guiding in the bore.

[0008] The invention will be discussed in greater detail hereinafter inconnection with the drawings, in which:

[0009]FIG. 1 is a diagrammatic illustration of a boring tool, which hasdouble cutting edges and indexable triangular-shaped inserts;

[0010]FIG. 2 is a diagrammatic illustration of an indexabletriangular-shaped insert;

[0011]FIGS. 3a to c are a top view and two side views of thetriangular-shaped insert according to FIG. 2;

[0012]FIG. 4 is an enlarged cutout section of a side view of theindexable insert with a support land in a schematic illustration withinthe drill geometry.

[0013] The boring tool illustrated in the drawings is designed as a coredrill with double cutting edges. The boring tool is designated for usein machine tools and has for this purpose a coupling shaft 12 forconnection to a not illustrated tool spindle, which coupling shaft 12 isdefined by a coupling flange 10 for a plane-surface bearing. Anelongated base body 14 is also connected to the coupling flange 10,which base body 14 has in the area of its face-side end two plate seats16, from where chip-conveying grooves 18 extend over the length of thebase body 14. Two trigon indexable inserts or cutting plates 20, whichare designed alike, are exchangeably arranged in the plate seats 16 andare secured on the base body 14 by fastening screws 22. The fasteningscrews are thereby screwed into the base body 14 starting out from thechip-conveying grooves essentially perpendicularly with respect to thedrill axis 24.

[0014] Each of the cutting plates has three major cutting edges 26, ofwhich one is active in the installed state. The major cutting edges 26have a roof-shaped tip 28, whereby the one leg 26′ of the major cuttingedge extends rectilinearly from the tip 28 toward the cutting-edgecorner 30, and the other leg 26″ has a further obtuse-angled bend 32toward the other cutting-edge corner 30. The angle of the roof-shapedtip 28 and the obtuse angle in the area of the bend 32 are therebydimensioned such that between the major cutting-edge leg 26′ and theadjacent bend 32 there is created an angle of 70° to 110°, andpreferably an angle of 90°. The bend 32, which is adjacent to therespective major cutting-edge leg 26′ through the cutting-edge corner30, forms in the installed state a minor cutting edge, which is followedby a guide and support land 34 for supporting the tool on the boringwall 36 (FIG. 4).

[0015] The cutting plate has furthermore a machining face 38 ending inthe chip-conveying groove 18, and a major flank 40 forming a cuttingwedge with the machining face. The minor cutting edge 32 is defined atits one longitudinal side by the common machining face 38, whereas theother side of the support land 34 is followed by a minor flank 42.

[0016] The support land 34 is defined by two support edges 44, 46, whichare arranged in a direction of rotation 43 of the tool at a distance sfrom each other, and which have over their entire length the same radiusdistance r₁ or r₂ from the tool axis 24, which radius distancecorresponds to the flight-circle radius of the tool. As can be seen fromFIG. 2 in connection with FIG. 4, the support edges 44, 46 extendparallel to the tool axis 24. However, the support edges 44, 46 havedifferent lengths in the illustrated exemplary embodiment in view of theadditional triangle land 48. The support land 34 as such is heredesigned as a flat surface parallel to the tool axis 24 (compare FIG. 3cand FIG. 4).

[0017] With the described measures, the tool can be supported withminimal friction on the boring wall 36 through the support edges 44, 46of the support land 34 during the drilling operation, and one and thesame cutting plate can be utilized for various bore radii r₁, r₂.

[0018] In summary the following is to be stated: The invention relatesto a cutting plate for tools rotating about a tool axis, and inparticular for boring tools with several cutting edges. The cuttingplate has a major cutting edge 26 and a minor cutting edge 32, whichminor cutting edge 32 is connected, in the extension of said majorcutting edge 26 radially outwardly through a cutting-edge corner 30, atan angle to said major cutting edge 26. A common machining face 33 isconnected to the one longitudinal side of the major cutting edge 26 andof the minor cutting edge 32, whereas a major flank 40 or a minor flank42 is connected to the other longitudinal side of the major cutting edge26 and of the minor cutting edge 32, which major flank 40 or minor flank42 defines a wedge angle with the machining face. In order to be able tosupport the tool with minimum friction on the boring wall 36, and inorder to thereby enable also in the case of far projecting tools anessentially vibration-free machining, it is suggested according to theinvention to arrange in the area of the minor cutting edge 32 a supportland 34, which is defined by two support edges 44, 46 arranged at adistance from each other in the direction of rotation of the tool,whereby the support edges have over their entire length the same radiusdistance r₁ or r₂ from the tool axis 24. The support edges 44, 46 areadvantageously aligned parallel to the tool axis 24, whereas the supportland is designed advantageously as a flat surface parallel to the toolaxis 24.

1. A cutting plate for tools rotating about a tool axis (24), comprisinga major cutting edge (26) and a minor cutting edge (32), which isconnected, in the extension of said major cutting edge radiallyoutwardly through a cutting-edge corner (30), at an angle to said majorcutting edge, comprising a common machining surface (38) connected toone longitudinal side of the major cutting edge (26) and of the minorcutting edge (32), and comprising a major flank (40) or a minor flank(42) connected to the other longitudinal side of the major cutting edge(26) or the minor cutting edge (32), and each defining a wedge anglewith the common machining face, characterized in that in the area of theminor cutting edge (32) there is arranged a support land (34), which isdefined by two support edges (44, 46) arranged at a distance from eachother in a direction of rotation of the tool, whereby the support edges(44, 46) have over their entire length the same radius distance (r₁ orr₂) from the tool axis (24).
 2. The cutting plate according to claim 1,characterized in that the support edges (44, 46) extend parallel to thetool axis (24).
 3. The cutting plate according to claim 1 or 2,characterized in that the support land (34) is designed as a flatsurface parallel to the tool axis (24).
 4. The cutting plate accordingto one of the claims 1 to 3, characterized in that the support land (24)has a length in its longitudinal extent aligned parallel to the toolaxis (24), which length corresponds at least to twice the distancebetween the support edges (44, 46).
 5. The cutting plate according toone of the claims 1 to 4, characterized in that the support edges (44,46) are spaced at a distance of 0.1 to 1.5 mm from each other.
 6. Thecutting plate according to one of the claims 1 to 5, characterized inthat the support land (34) extends between the support edges (44, 46)over a fraction of the cutting-plate thickness.
 7. The cutting plateaccording to one of the claims 1 to 6, characterized in that the supportland (34) extends in its longitudinal extent to the preferably roundedor faceted cutting-edge corner (30).
 8. The cutting plate according toone of the claims 1 to 7, characterized in that the major cutting edge(26′) and the connected minor cutting edge (32) define an angle of 70°to 110° in their longitudinal extent.
 9. The cutting plate according toone of the claims 1 to 8, characterized in that it is designed as anindexable insert with at least two major cutting edges (26) and supportlands (34) arranged at equal angular distances from each other.
 10. Thecutting plate according to claim 9, characterized in that it is designedas a trigon insert with three major cutting edges (26) having a roofshape with a point angle of 140° to 170°.
 11. The cutting plateaccording to claim 9 or 10, characterized in that support land (34),which belongs to a major cutting edge (26), is formed into the cornerarea of a major cutting edge (26) adjacent in a defined index direction.12. The cutting plate according to one of the claims 1 to 11,characterized in that the support edges (44, 46) are rounded or facetedessentially tangentially to the tool flight circle.